1. Field of the Invention
The present invention relates to a liquid quantity sensing device, and more particularly, to a contactorless and frictionless liquid quantity sensing device which has the merits of excellent durability, high precision, simple structure and low production cost.
2. Description of the Prior Art
FIG. 1 shows a schematic view of a liquid quantity sensing device which was disclosed by the inventor of the present invention patented in Sep. 18, 2001 in U.S. (Pat. No. 6,289,731). This sensing device for liquid quantity includes an inner tube 11, a coil 12, an outer tube 13, a magnetized float 14, a base 15, and a cap 16. The coil 12 is wound around the inner tube 11, and the magnetized float 14 is contained in the inner tube 11. the outer tube 13 is sleeved on the inner tube 11. the cap 16 is screwed on the inner tube 11 while the base 15 is attached to the bottom of the inner tube 11. Several seepage pores 151 are provided on the base 15 so as to allow liquid to seep in the inner tube 11. The top and bottom ends of the outer tube 13 are sealed with binder so as to protect the coil 12 wound around the inner tube 11. With this construction the liquid quantity can be measured by change of inductance in the coil 12 with respect to the position of the float 14 in the inner tube 11 corresponding to change of liquid level, and the amount of change of inductance is transformed by an electrical circuit into corresponding liquid quantity which is indicated on a page 17 connected outside of the sensing device. Soon the inventor has found out that his previous invention has following shortcomings:
1. The sensing device is composed of too many essential components which result in a complicated overall structure and an increased production cost.
2. It requires a tedious procedure to wind the coil around the inner tube, especially for a longer inner tube.
3. It is difficult to keep a precise clearance between the magnetized float and the inner tube to obtain an accurate measurement result.
For these defects noticeable on the inventor's prior invention, an improvement is seriously required.
The inventor has once more dedicated great efforts for years to studying and improving these defects and come up with an improved liquid quantity sensing device as provided in this invention to eliminate the defects mentioned above.